1. Field of the Invention
The present invention relates to an optical sheet and particularly to an optical sheet that can converge the incident light, manufacturing method thereof, and the backlight assembly using the same.
2. Description of the Prior Art
The large size LCD is usually equipped with direct-type backlight assembly. In the direct-type backlight assembly, the light sources are placed under the optical sheet. Please refer to FIG. 1, FIG. 1 shows the backlight assembly in Taiwan patent 1264596. The direct-type backlight assembly 1 includes a frame 11, a light source 12, a lamp cover 13, and a Fresnel lens 14. As shown in FIG. 1, after emitting from the light source 12, one part of light will enter the Fresnel lens 14 directly, and another part of light will be reflected to the Fresnel lens 14 by the lamp cover 13. After passing the Fresnel lens 14, the light will become parallel light. However, the Fresnel lens 14 applied in the direct-type backlight assembly 1 can't select the light according to the incident angle and passage of light, the energy emitting from the light source 12 can't be fully utilized.
Therefore, how to utilize the energy from light source efficiently by redesigning the Fresnel lens is an issue remained to be resolved in the industry.